Conventionally, a fuel feed apparatus has a fuel pump accommodated in a fuel tank. The fuel pump is applied with constant voltage to pump fuel to an internal combustion engine. The engine returns surplus fuel, which is not consumed in the engine, into the fuel tank through a pressure regulator provided in the vicinity of the engine. Alternatively, a fuel feed apparatus has a pressure regulator for controlling pressure of fuel discharged from a fuel pump, thereby supplying the pressure-controlled fuel by an amount consumed in the engine.
In such a fuel feed apparatus, the fuel pump regularly discharges the maximum amount of fuel equivalent to the capacity of the engine, and surplus fuel, which is not consumed by the engine, is exhausted from either the engine or the fuel feed apparatus. Consequently, the fuel pump consumes a large amount of energy. Furthermore, the surplus fuel is exhausted into the fuel tank, consequently, a large amount of fuel vapor is produced in the fuel tank produces.
A fuel feed apparatus, disclosed in JP-A-7-293397, includes a fuel pump for supplying fuel from a reservoir tank into each of injection valves provided respectively to cylinders. A pressure sensor is provided for detecting pressure of the fuel supplied from the reservoir tank. The fuel feed apparatus controls the fuel pump in accordance with an operation of the engine so as to maintain pressure of fuel in the reservoir tank at predetermined pressure. Such a fuel feed apparatus has a return-less structure, in which production of surplus fuel is suppressed by controlling an amount of fuel to correspond with the capacity of the engine.
In this fuel feed apparatus of JP-A-7-293397, one engine control unit (ECU) controls the fuel injection valve to control the operation of the engine, in addition to controlling the fuel pump. Consequently, the engine control unit is operated under heavy load.
By contrast, each of JP-A-2001-214826, JP-A-2001-214827 discloses a pump control unit (fuel pump controller: FPC). The FPC is provided separately from the engine control unit, thereby reducing load imposed on the engine control unit.
However, in each of the fuel feed apparatuses of JP-A-2001-214826, JP-A-2001-214827, the FPC controls the fuel pump in accordance with both the pressure of fuel discharged from the fuel pump and information, which indicates the operating condition of the engine, transmitted from the engine control unit. Accordingly, the FPC cannot control the fuel pump without the information transmitted from the engine control unit.